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Thread: To Barlow, or not to Barlow...that is the question?

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    Default To Barlow, or not to Barlow...that is the question?



    Hi All,

    Still pretty new here and I have a question about Barlow lenses. My scope came with a 'Deluxe 2x Barlow' that I use almost on every session. I actually have two questions -

    1. Is it better to have a combination of EPs (more expensive I know), to fill the magnification gaps or to use a Barlow?

    2. Is there a difference between the supplied with my scope 2 x Barlow and say a 2 x Televue Barlow for £100?

    Thanks all!

    Tel
    Telescopes: SW 250px FlexTube Dob GOTO, Celestron TravelScope 70, Binoculars: Revelation 15x70mm Eyepieces: 20mm ES68, 14mm,11mm,8.8mm, 6.7mm,4.7mm ES 82 degree,18mm Celestron X-Cel LX, ​32mm SW Plossl Accessories: TV Barlow, Telrad, SkyFi, Orion Ultrablock filter,#80a,#23A Filter, 'Asda' Cam.

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    Default Re: To Barlow, or not to Barlow...that is the question?

    Ok...Let me say this ..I have owned and used a heck of a lot of barlows over the years (got my first scope in 1953 as a cub scout) and never had one that was "awful" and was also not plastic...I do not think the average observer could sit down and look thru a dozen individual barlows and say which one was better then any of the others ...

    That said...I very rarely use a barlow..(I've got a lot of eyepieces) BUT I do admit that the barlow I carry in my eyepiece case that I use when using my refractors at star parties etc is a Televue..BUT the only reason I can honestly give for why I carry it is I guess "snob" appeal I find it no better nor worst then I do any of the others I have owned or used.. BTW... I did not buy the Televue it came with a used scope I purchased a few years ago...

    Just my opinion based on using my own very own OLD eyeballs....

    Bob G
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    Default Re: To Barlow, or not to Barlow...that is the question?

    Thanks Bob!

    The reason I am unsure is that I bought a new EP - a Celestron X-Cel LX 7mm and it really is head and shoulders above the 'stock' EPs. However, when I used it on Jupiter with the Barlow, it didn't quite see as sharp as the EP on its own. I know there is less light etc with a Barlow, but I didn't really notice any difference with the standard EPs with a Barlow in quality. Maybe it's just me....


    Tel
    Telescopes: SW 250px FlexTube Dob GOTO, Celestron TravelScope 70, Binoculars: Revelation 15x70mm Eyepieces: 20mm ES68, 14mm,11mm,8.8mm, 6.7mm,4.7mm ES 82 degree,18mm Celestron X-Cel LX, ​32mm SW Plossl Accessories: TV Barlow, Telrad, SkyFi, Orion Ultrablock filter,#80a,#23A Filter, 'Asda' Cam.

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    Default Re: To Barlow, or not to Barlow...that is the question?

    1. Is it better to have a combination of EPs (more expensive I know), to fill the magnification gaps or to use a Barlow?

    It is best to have a range of magnifications and fields of view so that each object can be properly framed.
    This can be achieved with a number of individual EPs (5+) or it can be achieved with careful selection of fewer EPs (3) and a Barlow/PowerMate.

    2. Is there a difference between the supplied with my scope 2 x Barlow and say a 2 x Televue Barlow for £100?

    Not much, if any.

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    Default Re: To Barlow, or not to Barlow...that is the question?

    i use my barlow for viewing planets and the moon, i like using just the eyepiece of the mag i want mainly because the barlow dims down the image a bit, which is why i like using it on planets.

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    Default Re: To Barlow, or not to Barlow...that is the question?

    Same answer as Bob... I usually use straight eyepieces, without a barlow.
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    Default Re: To Barlow, or not to Barlow...that is the question?

    Hi Tel,

    I can't answer the question, but can give an observation based opinion . I am using a 5" acrho refractor with a 3x, 4 element, non-boutique Barlow (although pricey). In retrospect, I should have just bought a quality higher power, wide field EP. I think you are better going with a variety of wide field EPs than a Barlow. My Barlow tends to darken the view and diminish clarity. If you are not dealing with an achro frac, there probably wouldn't be much difference in your stock Barlow vs. Televeiw. There would be a difference in the craftmanship and materials. Some of the higher end barlows claim to reduce CA in achros, I can't speak to that. Depending on the seeing, I really enjoy my 3x Barlow for viewing the moon, Jupiter, and Saturn. If the seeing isn't good, the barlow is useless. The thing that is somewhat annoying with my Barlow (and not having a drive motor on my GEM) is the frequent chasing due to the narrow field. I find uses for my Barlow, so I wouldn't say it was a waste of money, but I should have went with an EP (wide field) instead.

    Good Luck,
    Rich
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    Default Re: To Barlow, or not to Barlow...that is the question?

    Quote Originally Posted by Telstar View Post
    The reason I am unsure is that I bought a new EP - a Celestron X-Cel LX 7mm and it really is head and shoulders above the 'stock' EPs. However, when I used it on Jupiter with the Barlow, it didn't quite see as sharp as the EP on its own. I know there is less light etc with a Barlow, but I didn't really notice any difference with the standard EPs with a Barlow in quality. Maybe it's just me....

    Tel
    Tel,

    Your Skywatcher Explorer130p is an f/5 scope with a focal length of 650mm. Theoretically your maximum magnification should be 130x.
    You will achieve this with a 5mm eyepiece.

    In barlowing your 7mm eyepiece you've pushed the magnification to 185x. (a Barlowed 7mm is the equivalent of using a 3.5mm eyepiece).
    So focal length 650 divided by 3.5 = 185.

    185x you will only be able to use when conditions are pretty nigh perfect. If your view wasn't quite as sharp as you would have liked, then I suspect your viewing conditions were to blame.

    Alec.
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    Default Re: To Barlow, or not to Barlow...that is the question?

    Quote Originally Posted by Alec in France View Post
    Tel,

    Your Skywatcher Explorer130p is an f/5 scope with a focal length of 650mm. Theoretically your maximum magnification should be 130x.
    You will achieve this with a 5mm eyepiece.

    In barlowing your 7mm eyepiece you've pushed the magnification to 185x. (a Barlowed 7mm is the equivalent of using a 3.5mm eyepiece).
    So focal length 650 divided by 3.5 = 185.

    185x you will only be able to use when conditions are pretty nigh perfect. If your view wasn't quite as sharp as you would have liked, then I suspect your viewing conditions were to blame.

    Alec.
    Thanks Alec. I thought thought that the maximum magnification was 260x, though i would need perfect viewing conditions for that. I worked on the assumption that the best I will get is around 70% of the max due to LP etc, so I figured the 7mm would Barlow perfectly? However, you are right that the 10mm stock EP Barlowed looked clearer....130x, so Maybe I got confused...

    I think I am going to just expand my EPs and not use the Barlow - that way there is less glass to dim the image I see?

    Tel
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    Default Re: To Barlow, or not to Barlow...that is the question?

    A quick run of the numbers seems to say you haven't passed the "maximum" theoretical magnification for either of your scopes. With the 7mm e/p you are getting about 57x. So double that with the Barlow. I would say to try that combination again on a few nights and see if the seeing wasn't all that great the first time you used it..
    Last edited by Tenutz; 10-05-2012 at 07:18 PM. Reason: needed added for clarity.

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